How to Make Vinyl Figures?
A Comprehensive Step-by-Step Guide to Rotocasting Vinyl Figures
2026-04-08
Complete Process Specification for Roto-casting Vinyl Figures
Introduction
This document is based on over 10 years of experience and engineering data from Demeng Toy in the customized production of vinyl figures. It systematically outlines the key technical points of the entire process, from mold making, vinyl molding, post-processing (injection, spraying, pad printing) to quality control. All parameters and strategies have been validated through thousands of artistic design practices, making them suitable for mass production environments of vinyl figures.
Chapter 1 – Vinyl Mold Manufacturing
1.1 Standard Workflow
Drawing → 3D modeling (ZBrush/Blender/3ds Max) → PU prototype printing & sanding → Master mold (copper) → Production mold (electroforming) → Production skin (mass production mold)
1.2 Key Control Points
Shrinkage compensation – Due to linear shrinkage of PVC during cooling, the master skin must be 3–4% larger than the production skin. Actual shrinkage varies with formulation: higher PVC fine powder (810) or higher plasticizer (white oil) content increases shrinkage. A dedicated shrinkage test plaque should be produced before vinyl parts mass production, and the compensation factor adjusted accordingly.
Mold wall thickness uniformity – Electroforming must control copper deposition thickness to avoid local thick/thin areas. Any non-uniformity directly causes reverse thickness deviation in the vinyl part (thick mold wall → thin vinyl area) and cannot be fully corrected by downstream processes.
Chapter 2 – Rotocasting Process
2.1 Material Formulation (Reference BOM)
PVC powders – Fine powder 810 (surface finish) + Coarse powder C65V (structural strength)
Plasticizer system – White oil (flexibility), TXIB, 57° hard oil (cold resistance & set), ED-S heat stabilizer (prevents yellowing)
Additives – CE-116 stabilizer (prevents decomposition), mold release agent
Environmental compliance note – Phthalate plasticizers and heavy metal stabilizers (e.g. lead, barium) in the above formulation must comply with destination market regulations (e.g. EN71-3, ASTM F963). Pre-production third-party testing is required: total phthalates ≤0.1%, heavy metal migration within limits.
2.2 Process Parameters
Slush oven – Temperature 250–280°C, time baseline 2 minutes. This baseline applies to conventional wall thickness (3–4 mm) and medium weight. For oversized figures (height >40 cm) or very thin walls (<1.5 mm), a DOE (Design of Experiments) must be performed to determine optimal slushing time and mold rotation angle.
Post-curing (tunnel oven) – Temperature approx. 100°C, time 10 minutes. Relieves internal stress and stabilizes shape.
2.3 Cooling Method
After demolding, vinyl parts must never be exposed directly to cold air or dipped in cold water. They shall be placed on natural cooling racks or fed through a stepped cooling oven (80°C → 50°C → ambient), staying at least 5 minutes at each stage. Rapid cooling induces high internal stress, causing warpage or dimensional deviation.
2.4 Common Defects and Countermeasures
Defect | Root Cause | Solution |
Uneven wall thickness | Non uniform mold wall thickness | Wrap tin sheet on thin mold areas (which cause thick vinyl) to locally reduce temperature; for severe cases, rework mold |
Uncured (raw) vinyl | Insufficient temperature or time | Increase oven temperature or time; check for cold zones inside oven |
Warpage | Excessive cooling rate | Use stepped cooling or natural cooling; verify tunnel oven temperature uniformity |
Chapter 3 – Post-Processing Chain
3.1 Injection Molding (Rigid Components)
Used for hard parts (eyes, bases). Reject defects: flow marks, bubbles, sink marks, short shots. Gate removal must be done with gate cutters or a sharp knife – never pull the gate, as this causes stress whitening or fracture.
3.2 Assembly of Rotocast Parts with Injection-Molded Parts
Common assembly methods: snap-fit or ultrasonic welding.
Snap-fit – Root radius must be ≥0.3 mm to avoid stress concentration and cracking.
Ultrasonic welding – Pressure 0.2–0.4 MPa, time 0.5–1.2 seconds. First-article pull test (≥15 kgf) required for each batch.
3.3 Spray Painting
3.3.1 Paint to Thinner Ratio (by volume)
Black paint : thinner = 1 : 1
White paint : thinner = 1 : 1.2
Standard colors (yellow/red/blue) : thinner = 1 : 1.7
3.3.2 Solvent System Differentiation
Substrate | Recommended thinner | Prohibition |
Rigid plastic (ABS/GPPS) | A580A, cyclohexanone, 414 anti blush | Never use soft plastic thinner (contains MEK/acetone) – will etch the surface |
Soft PVC (rotocast) | A760 wash thinner, MEK (563), acetone + wash thinner blend | Rigid-plastic thinner is relatively safe for wiping oil stains |
3.3.3 Special Environmental Countermeasures
Blushing (whitening) in high humidity / rainy days – Add 5–10% cyclohexanone (high boiling point solvent) to the paint to extend leveling time and prevent moisture condensation.
Dull finish (lack of gloss) – Lightly spray a mist coat of cyclohexanone over the dry dull surface; it micro-dissolves the surface and restores gloss.
3.3.4 Standard Time & Paint Consumption
Standard time = painting time + mold cleaning time (amortized per shot) + allowance (typically 20% of painting time for fatigue / personal needs)
Paint consumption – 1 liter of mixed paint covers approximately 7 spray gun loads (depending on nozzle size and air pressure)
3.4 Pad Printing
Used for fine details (pupils, logos). Key controls:
Ink adhesion – 3M 610 tape peel test: peeled area shall not exceed 4% of the total printed area.
Registration accuracy – allowable shift ≤0.2 mm.
Reject defects: blurring, fuzzing, missing prints, cracks, etc.
Chapter 4 – Quality Inspection Criteria
4.1 Rotocast Parts
Not allowed: foreign matter, uncured material, bubbles, scratches, warpage, dents.
4.2 Spray-Painted Parts
Not allowed: oil contamination, peeling (lifting), overspray, scratches, orange peel, incomplete coverage, bare substrate, cracks, bubbles, missing process steps.
Root cause of paint peeling – Oil residue on the part surface before painting. Parts must be wiped with white spirit or rigid-plastic thinner prior to painting.
4.3 Pad-Printed Parts
Not allowed: incorrect color/luster, misregistration/offset/incomplete coverage, blurring, fuzzing, peeling, ink lift >4%, bubbles, cracks, scratches, ink stains, missing prints.
4.4 Batch Adhesion Testing
Perform a tape peel test every 200 pcs. After three consecutive passing batches, interval may be extended to 500 pcs. If any batch shows >4% ink lift, stop production immediately and investigate paint/thinner ratio, baking temperature, or part cleanliness.
Chapter 5 – Production Engineering & Process Management
5.1 Pre-Production Capacity Assessment
Spray line load = total parts to spray ÷ (daily output per gun × number of guns)
Total paint consumption = total area to spray × consumption per unit area × (1 + waste rate)
Manpower – based on standard time and daily target output, calculate required painters and mold cleaners
5.2 Complete Production Workflow
3D modeling → PU prototype & approval → Master mold (including shrinkage test plaque) → Production mold electroforming → Rotocasting (oven temperature/time per DOE) → Stepped cooling → Trimming (gate removal) → Assembly of injection parts (snap/ultrasonic) → Spray painting / pad printing → 100% inspection (per Chapter 4) → Batch adhesion test → Packing & shipping
5.3 Environmental & Compliance Records
On rainy days, record the amount of cyclohexanone added to paint, along with ambient temperature and humidity.
For each raw material batch (PVC powders, plasticizers, paints, thinners), retain COA (Certificate of Analysis) and third-party environmental test reports (at least every 6 months).
Chapter 6 – Common Problem Quick Reference
Problem | Direct Cause | Action |
Locally thin vinyl | Thick mold wall in that area | Wrap tin sheet on mold to reduce local temperature |
Locally thick vinyl | Thin mold wall in that area | Cannot wrap tin sheet; mold must be reworked |
Uncured vinyl | Insufficient oven temperature/time | Increase temperature/time; check for cold zones |
Warpage | Too rapid cooling | Use stepped or natural cooling |
Paint peeling (lifting) | Oil residue on part | Wipe part with white spirit before painting |
Ink lift >4% | Poor adhesion | Check paint/thinner ratio, baking temperature; change ink |
Snap fit crack | Stress concentration at root | Add radius ≥0.3 mm; reduce ultrasonic welding pressure |
Blushing in rainy weather | High humidity | Add 5–10% cyclohexanone to paint |
Appendix – Recommended Test Methods
Shrinkage test plaque – Mold a 100×100×3 mm standard square. After rotocasting and cooling for 24 hours, measure actual dimensions to calculate shrinkage.
Adhesion tape test – Use 3M 610 tape, length approx. 75 mm. Apply over the printed area, roll down with a rubber roller three times, wait 1 minute, then pull off at 90° angle.
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